Ward-leonard control for wire spooler



Dec. 17, 1957 H. A. DICKERSON 2,

WARD-LEONARD CONTROL FOR WIRE SPOOLER Filed Nov. 10, 1953 WDM DrawingMachine To Drawing Machine Motor Field Rheoiot INVENTOR Henry A.Dickerson.

ATT

United States Patent 2,817,049 WARD-LEONARD CONTROL FOR WIRE SPOOLERHenry A. Dickerson, Snyder, N. Y., assignor to Westinghouse ElectricCorporation, East Pittsburgh, Pro, a corporation of PennsylvaniaApplication November 10, 1953, Serial No. 391,338

13 Claims. (Cl. 318146) My invention relates to electric systems ofcontrol, and

more particularly to systems of control for controlling the operatingcharacteristics of a direct current motor and generator connected in aloop circuit.

A particular application of my system of control is for the drive of awire drawing machine spooler, which is a device located at the outputend of a wire drawing machine for taking the finished wire from the wiredrawing machine at a definite value of tension and winding it in evenlayers of uniform tightness on a spool. My invention is not limited tothis application but since the merits of my invention may be effectivelyexplained in connection with the application mentioned, the disclosurewill proceed with the particular application in mind.

To better understand the problems involved, a very brief description ofthe wire drawing machine in relation to the spooler drive may behelpful.

In a wire drawing machine the wire is pulled through dies withsuccessively smaller holes by powered capstans to reduce the Wire incross section and increase it in length. The capstans are locatedbetween the various dies so that they pull the wire from one die andsupply it to the next die in line. The tension required is developed bythe wire friction of one or more turns about the capstan. The last ofthe capstans pulls the wire from the last die and delivers the wire tothe spooler drum.

While the take-away tension between the last capstan and spooler mayvary over a fair range, a departure too great from the desired range cancause trouble. If the spooling tension is too high the wire pulls tootightly on the spool, causing a turn to slip down between turns of aprevious layer and lock in. This prevents proper unwinding of the wirefrom the spool, and causes wire breakage and scrapping of the spool inmany instances.

If the wire tension between capstan and spooler is too low, the capstancannot develop sufficient pull on the entering wire to pull it throughthe finish die. Slip will then occur on thefinish capstan causing thewire to jump and chatter which may cause the wire to snarl and break.

One broad object of my invention is the provision of a system of controlfor a motor generator loop to provide the proper torque characteristicsfor the motor, to incidentally provide for the application had in' minda proper tension in the wire between the last capstan of a wire drawingmachine and the spooler drum.

Another broad object is the provision of proper wire tension duringspool build-up, drawing machine acceleration and drawing machinedeceleration.

It is also an object of my invention to provide proper torque on thespooler motor when at Zero speed to provide proper stall tension.

The only mechanical connection between the separately powered spoolerdrive and the wire drawing machine .is throughthe'wire being spooled. Tocorrelate the speed vI provide. electro-mechanical interconnectionsbetween the drives to match the spooler speed, during normal running andduring acceleration and deceleration, to the speed of the drawingmachine. Such correlation alone is, however, not enough because wiresizes vary, the starting and stopping may occur when the spool isanywhere between an empty spool and a full spool, the accelerating ratesmay be adjustable, and the spool capacity may be changed.

One broad object of my invention is the provision in an electric controlfor a direct current motor to compensate for changes of inertia,accelerating rate, IR drop and speed change.

Other objects of my invention will become more apparent from a study ofthe following specification and the accompanying drawing, in which thesingle figure is a diagrammatic showing of my invention as applied to amotor operating a load, as a wire spooler.

The generator is provided with a shunt field winding SF and a voltageregulating field winding RF. This regulating field winding RF isconnected in a loop circuit with the armature of the pilot generator andthe armature of the reel, or main generator G. The connection is suchthat when there is a difference in the output voltages between these twogenerators, a current flows in the regulating field winding RF in such adirection to cause the main generator voltage to follow the pilotgenerator voltage.

In the drawing IM represents the constant speed motor for driving thegenerator G, which generator G is connected in a loop circuit with themotor M driving the spool S for receiving the wire W from the lastcapstan C of the wire drawing machine WDM. A pilot generator PG ismechanically coupled to the last capstan C. Since the pilot generator PGis excited at a selected fixed value by its field winding PF connectedas shown through the rheostat R directly to the fixed voltage directcurrent supply buses 1 and 6, its voltage output is substantiallydirectly proportional to the speed of the last capstan C of the wiredrawing machine WDM.

The motor for driving the spool S is excited by its field winding MFwhich is subject to the output of the magnetic amplifier MA. Thismagnetic amplifier does, however, not take over the control of the fieldwinding until its output is in excess of a selected value determined bythe direct current voltages supplied through rheostat 2 from the buses 1and at the direct current terminals of the full-wave rectifier PR. Thecircuit for field winding MF from the buses 1 and 6 may be traced frombus 1 through rheostat 2, terminal 3, field winding MP through theself-exciting windings 4 and 5 of the magnetic amplifier MA to bus 6.

To more readily understand my contribution to the art, a briefexplanation of the starting and operating functions of the showing inthe figure may be helpful.

To start the system, assuming the generator G is running at full speed,the start push button switch 8 is depressed whereupon a circuit isestablished from bus 1 through the stop switch 7, the upper contacts ofstart switch 8, the actuating coil 9 of the dynamic braking contactor DBto bus 6. Operation of the dynamic braking contactor closes contacts 11and opens contacts 12 to open the circuit of the dynamic brakingresistor DBR. Closure of contacts 11 establishes a circuit from theupper contacts of the start switch 8, through the actuating coil 10 of:contactor SM, the contacts 11, the lower contacts 13 of the startswitch 8 to bus 6. The contacts 13 are in parallel to the broken wireswitch BWS and other safety switches, not shown. The contactor SM afterit operates holds itself in through contacts 14 and closes contacts 16and 18 simultaneously and a moment later closes contacts 19 to efiectthe starting of the wire drawing machine a moment after the spoolermotor has subjected the wire to tension. 111 case of wire breakageswitch BWS opens action .2 to stop the system. The closure of contacts18 closes the circuit shown for the brake coil to decouple the brakefrom its brake drum to permit the motor M to start the spool S.

The closure of contacts 16 establishes a circuit from the upper terminalof generator G through contacts 16, the armature of motor M, resistor 17to the lower terminal of the generator G. The motor M having its fieldMF excited will, if the voltage ofgenerator G is up, place some torqueon the spool shaft. The voltage of generator G is, however, dependent onthe regulating effect of the pilot generator PG and the excitation theregulating field RF receives from the generators G and PG which are in aloop circuit with the regulating field RF.

In a simple loop circuit for the regulating field winding RF as justexplained certain steady state and dynamic errors exist, the magnitudesof such errors depending on system gain, regulating circuit timeconstant, power loop circuit IR-drop, and the rate of change of thepilot generator voltage.

In my control system I use compensating voltage in the loop circuitproduced by the flow of controlled external current through a lowresistance resistor connected in the loop circuit of the regulatingfield RF. In addition, this system I interconnect with the regulatingapparatus of the tension winder to ipro'duce a selected stall tensionand/ or spooler jogging.

Stall tension This function is achieved when the motor M isat, or near,zero speed and the constant tension regulator, namely the controlledmagnetic amplifier control, operating on the field MP, is ineffectivebecause of the low value or absence of E. M. F. from motor M. For thiscondition the pilot generator voltage, being proportional to the wirespeed, will be at or near zero and the voltage of generator G, beingmade tomatch the voltage of the pilot generator 'by the action of thereg-ulatingfield winding RF, will be too low to cause an effectivecurrent to how in the armature loop circuit of the motor M and generatorG. With the control I provide, a current is caused to flow from terminal1th through the closed contacts 101 of the decelerating contactor Dec,the adjustable resistor 102, conductor 1G3, resistor 104, which resistor104 may be of relatively low resistance value, through the back contacts105 of the decelerating contactor Dec, to the terminal 106. This flow ofcurrent through resistor 104 produces a voltage drop. This voltage drop,being in the regulator circuit, appears as an E. M. F. to the field RFand a current flows in. this field winding until the voltage ofgenerator G balances the voltage appearing across the resistor 104. Thegenerator voltage is then strong enough to cause an effective current toflow in the armature of motor M. This current interacting with theminimum spooler motor field excitation provided by field winding MF:produces a motor torque to provide stall tension and/ or spoolerjogging. The magnitude of the torque can be varied by adjustment of tap167 on -the stall tension rheostat 1132.

It should be noted that tap 137 is ganged with the rheostat of thepattern winding rheostat in such a manner that when the excitation ofthe pattern winding i increased the stall tension is increased also. Byproportioning the magnitude of the stall current so that its effect inthe tension regulator control is always less than that of the patternwinding, the regulator (the magnetic amplifier regulator) will remain atthe minimum output condition. This is desirable for'the followingreasons.

(1) If the tension regulator saturated when the stall current wasincreased the stall torque would be increased heyond desirable limitswhen the motor field was increased.

(2) Minimum regulator outputis a desirable condition at the beginning ofthe accelerating period that follows the application of stall tension.

(3) Minimum field strength allows a maximum stall current to flow for agiven stall torque. This allows effective IR compensation as outlined inthe following:

IR c0mpcnsati0n.The stall voltage produced across the resistor 104 bythe external current is maintained during the accelerating and runningperiods. Since this voltage can cause a stall current to flow that isslightly less in magnitude and in step with the running currentcontrolled by the pattern field strength it furnishes an effective IRcompensation.

Inertia c0mpcnsation.During accelerating or decelerating periods thetension regulator of the standard spooler scheme changes the spoolermotor armature current to increase or decrease motor torque to provideinertia compensation to accelerate or decel-erate the spooler and itsload. This change in controlled armature current changes the IR drop inthe spooler motor armature loop. The proposed scheme, using additionalcontacts on the accelerating and decelerating relays provided for thetension regulator, in conjunction with variable resistances in a circuitparallel to the stall tension adjusting rheostat, increases or decreasesthe voltage appearing across the resistor 104 to provide improved IRcompensation during these periods when inertia compensation is required.Also, if the compensating voltages are made higher than required for IRcompensation alone, they will, (1) compensate for the inductive time lagin the regulator field RF of the generator and, (2) cause the spoolergenerator output voltage to lead a change in pilot generator voltage andthereby allow the tension regulator operating on the motor field to bemore effective during the periods when inertia compensation is required.

Assuming that the voltage of generator G is such that the motor Maccelerates, as it does so, the accelerating contactor is eneregized bya circuit that may be traced from bus 1 through contacts 20 of theacceleration switch AS, actuating coil it of the accelerating contactorAct: to bus 6.

This contactor Acc closes its contacts 188 to alter the regulatingcomponent on field RF in response to acceleration by connecting anadjustable resistor 109 in parallel to resistor I92. Contactor Acc alsocloses contacts 22 and 23 to place a voltage across the inertiacompensation potentiometer P by a circuit that may be traced from bus 1through adjustable resistor 24, contacts 22, potentiometer P, contacts23 to bus 6. This energizes windings 2% and 3t) cumulatively withrespect to the pattern windings 33 and 37. to increase the torque of themotor M to maintain wire' tension.

When the decelerating contactor Dec is energized by closure of contacts25, this contactor Dec closes contacts as and 27, to energizepotentiometer P with reverse polarity, and closes contacts I10 and openscontacts 101 and 105 to reverse the control effect for the regulatingfield RF from the terminals and 106 through the rheostat 111.

The tap 28 connects the inertia compensating control windings 29 and 30of the magnetic amplifier to the potentiometer P. This energizeswindings 29 and 30 so as to reduce the torque of motor M. The patternfield windings 32 and 33 are differential with respect to the mainwindings 39 and 40, and are connected directly to buses 1 and 6 throughrheostat 31.

The control windings 34 and 35 are connected directly across resistor 17to produce a control effect cumulative with respect to main windings 39and 40, and proportional to armature current.

The circuit for the main windings of the magnetic amplifier may, for onehalf wave of alternating current, be traced from the upper terminal ofthe secondary of transformer T through rectifier 36, field winding MFfrom left to right, self-exciting feed-back windings 4 and 5 which arecumulative with respect to-windings' 39' and 40, bus 6, rectifiers 37and 38, and winding 39 to the lower terminal of transformer T.

Anti-hunt windings 44 and 45 on the magnetic amplifier MA are connectedin shunt with the series connection of windings 4 and 5 and fieldwinding MF, difierentially with respect to the main windings 39 and 40,for stabilizing operation of the amplifier.

For the second half wave the circuit is from the lower terminal of thesecondary of transformeg T through main winding 40, rectifiers 41 and42, field winding MF from left to right through the feed-back windings 4and 5, bus 6, and rectifier 43 to the upper transformer terminal.

During normal operation the voltage of the generator G is matchedagainst the voltage of the pilot generator PG to regulate the voltageapplied to the armature of motor M. Tension is maintained by magneticamplifier MA, which increases the voltage applied to the field MP inresponse to an increase in energization of windings 34 and 35 upon anincrease in armature current and thus reduces the tension on the wire,restoring the armature current to normal. The value of current for whichthe amplifier MA is set is determined by the pattern windings 32 and 33,and is increased and decreased by the inertia compensation windings 29and 30 during acceleration and deceleration respectively, so as tomaintain wire tension.

From the control disclosed, it is apparent that-I have provided, amongother novel and valuable features constituting part of my invention,for:

(1) The elimination of rotating machines heretofore used for similarpurposes.

(2) Adjustable stall tension at standstill and low spooling speeds whenthe tension regulator is inefiective.

(3) Effective power circuit IR compensation during running periodsfurnished by the same control components that provide stall tension.

(4) Additional compensation during accelerating and decelerating periodsfor increased IR drops, inductive time lags and inertia compensation.

While I have shown but one embodiment and one application of myinvention, modifications may readily be devised by those skilled in theart, after having had the benefit of my disclosure, without departingfrom the spirit of my invention.

I claim as my invention:

1. In a Ward-Leonard control including a generator and a motor connectedin a loop circuit, in combination, a field winding for the motor, animpedance in the loop circuit of the motor and generator, a magneticamplifier for controlling the energization of the motor field winding, acontrol winding, responsive to the motor armature current, for saidmagnetic amplifier, a pilot generator, a generator field winding, acontrol loop circuit including the armature of the generator, thegenerator field winding, and the armature of the pilot generator, andmeans for providing a voltage drop in said control loop circuit to alterthe excitation of the generator field winding.

2. In a Ward-Leonard control including a generator and a motor connectedin a loop circuit, in combination, a field winding for the motor, animpedance in the loop circuit of the motor and generator, a magneticamplifier for controlling the energization of the motor field winding, acontrol winding, responsive to the motor armature current, for saidmagnetic amplifier, a pilot generator, a generator field winding, acontrol loop circuit including the armature of the generator, thegenerator field winding, and the armature of the pilot generator, aresistor in said control loop circuit, and means for providing a voltagedrop in said control loop circuit across said resistor to alter theexcitation of the generator field windmg.

3. In a Ward-Leonard control including a main generator and main motorhaving their armature windings connected in a loop circuit, incombination, a field winding for the generator, an impedance, a pilotgenerator, operable in response to the speed of the main motor, havingits armature winding connected in a control loop 6 circuit with the maingenerator armature, the generator field winding, and said resistance,and means for producing a voltage drop across said impedance from anexternal voltage source.

4. In a Ward-Leonard control including a main generator and main motorhaving their armature windings connected in a loop circuit, incombination, a field winding for the generator, an impedance, a pilotgenerator, operable in response to the speed of the main motor, havingits armature winding connected in a control loop circuit with the maingenerator armature, the generator field winding, and said resistance,means for producing a voltage drop across said impedance from anexternal voltage source, a field winding for said motor, and controlmeans for energizing said motor field winding as a function of thearmature current of the motor and as a function of the voltage drop fromsaid external source produced in said impedance.

5. In a control for a direct-current motor having an armature, a maingenerator having an armature connected in circuit with the motorarmature to supply the principal energy to energize the motor armature,voltage producing means responsive to motor speed connected across saidmain generator, and field winding means on said main generator includinga difierential field winding connected in series with said voltageproducing means across'sai main generator.

6. In a control for a direct-current motor, a main generator having anarmature circuit connected to energize the motor armature, voltageproducing means responsive to motor speed connected across said maingenerator, field winding means on said main generator including adilferential field winding connected in series with said voltageproducing means across said main generator, impedance means connected inseries with said voltage producing means across said main generator, andcircuit means connected with said impedance means for applying anelectrical quantity thereto.

7. In a control for a machine operated by a directcurrent motor havingan armature winding and a field winding, the combination of a generatorhaving an armature winding connected to the motor armature winding, amagnetic amplifier having a direct current output circuit connected tothe motor field winding, control winding means on said magneticamplifier, adjustable impedance means connected to said control winding,and acceleration switch means operable to effect acceleration anddeceleration of said machine and connected to said impedance means toreversibly energize said impedance means.

8. In a control for a machine operated by a directcurrent motor havingan armature winding and a field winding, the combination of, a generatorhaving an armature Winding connected to the motor armature winding,voltage producing means connected with said motor for producing avoltage proportional to motor speed, circuit means including adifferential field winding on said generator and an impedance deviceconnecting said voltage producing means across said generator, amagnetic amplifier having a direct-current output circuit connected tosaid motor field winding, control winding means on said magneticamplifier, adjustable impedance means connected to said control windingmeans, adjustable impedance means connected to said impedance device,means mechanically connecting both said adjustable impedance means, andmeans for energizing both said adjustable impedance means.

9. In a control for a machine operated .by a direct-current motor havingan armature winding and a field winding, the combination of, a generatorhaving an armature winding connected to the motor armature winding,voltage producing means connected with said motor for producing avoltage proportional to motor speed, circuit means including adifferential field winding on said generator and an impedance deviceconnecting said voltage producing means across said generator, amagnetic "amplifier having a. direct-current output circuit connected tosaid motor field winding, control winding means on said magneticamplifier, adjustable impedance means connected to saidcontrolwindingmeans, adjustable impedance means'connected to saidimpedance device, means mechanically connecting both said adjustableimpedance means, means for energizing both'said adjustable impedancemeans and acceleration switch means operable 'to eifect acceleration anddeceleration of said machine and connected to said impedance means toreversibly energize said first-named adjustable impedance means.

10. Ina direct-current motor control, a motor'having an armature windingand a field winding, a main generator having an armature winding andfield winding means including adiiferential field winding, circuit meansconnecting the generator armature-winding to the motor armature winding,a pilot-generator connected to and driven by said motor, an impedancedevice, circuit means connecting said differential field winding, saidpilot generator and said impedance device across said generator armaturewinding, magnetic amplifier means having a direct-current output circuitconnected to energize said motor field winding and having controlwinding means, andcircuit meansconnected with said impedance device andwith said control Winding means for simultaneously affecting a controlthereof.

11. In a direct-current motor control, a motor having an armaturewinding and a field winding, a main generator havingan armature windingand field winding means including a difierential field winding, circuitmeans connecting the generator armature winding to the motor armaturewinding, a pilot generator connected to and driven by said motor, animpedance device, circuit means connecting said differential fieldwinding, said pilot generator and said impedance device across saidgenerator armature winding, magnetic amplifier means having adirect-current output circuit connected to energize said motor fieldwinding and having control winding means, said control winding meanscomprising at least two control windings, circuit means connecting onecontrol winding to said motor armature to be energ zed in dependence ofmotor armature current, an adjustable impedance connected to the othercontrol winding, a second adjustable impedance connected to saidimpedance device, and means mechanically connecting said firstmentionedand said second adjustable impedances to provide simultaneousadjustment.

12. In a direct-current motor control, a motor having an armaturewinding and a field Winding, a main generator having an armature windingand field winding means including a differential field winding, circuitmeans connecting the generator armature winding to the motor armaturewinding, a pilot generator connected to and driven by said motor, animpedance device, circuit means connecting said differential fieldwinding, said pilot generator and said impedance device across saidgenerator armature winding, magnetic amplifier means having adirect-current output circuit connected to energize said motor fieldwinding and having control winding means, said control Winding meanscomprising at least two control windings, circuit means connecting onecontrol winding to said motor armature to be energized in dependence ofmotor armature current, an adjustable impedance connected to the othercontrol winding, a second adjustable impedance connected to saidimpedance device, means mechanically connecting said first-mentioned andsaid second adjustable impedances to provide simultaneous adjustment,and means including reversing switch means connected to said first-namedadjustable impedance to reversibly energize said first-named adjustableimpedance.

13. In a direct-current motor control, a motor having an armaturewinding and a field winding, 21 main generator having an armaturewinding and field winding means including a differential field winding,circuit means connecting the generator armature winding to the motorarmature winding, a pilot generator connected to and driven bysaidmotor, an impedance device, circuit means connecting saiddifferential field winding, said pilot generator and said impedancedevice across said generator armature winding, magnetic amplifier meanshaving a direct-current output circuit connected to energize said motorfield winding and having control winding means, said control windingmeans comprising at least two control windings, circuit means connectingone control winding to said motor armature to be energized in dependenceof motor armature current, an adjustable impedance connected to theother control winding, a second adjustable impedance connected to saidimpedance device, means mechanically connecting said first-mentioned andsaid second adjustable impedances to provide simultaneous adjustment,means including reversing switch means connected to said first-namedadjustable impedance to reversibly energize said first-named adjustableimpedance, and an acceleration switch disposed to effect accelerationand deceleration of said motor and connected to said reversing switchmeans to control said reversing switch means.

References Cited in the file of this patent UNITED STATES PATENTS

